Blake Shelton has gushed about his girlfriend Gwen Stefani, describing her as "the coolest girl in the world".

Blake Shelton "loves" the duet he wrote with Gwen Stefani for his upcoming album.

The country music star and his pop star girlfriend Gwen have collaborated on song Go Ahead and Break My Heart, which will be featured on Blake's new album If I'm Honest.

And while Blake confessed last August (15), before the pair started dating, that he never saw himself "sitting down and writing songs" with the blonde beauty, he has since changed his tune on the idea of collaborations.

"We were at a point where it's like, 'Do we want to go there? What will people think?' And then we finally just got to the point where it's like, 'You know what? I don't give a s**t," he told PEOPLE magazine at an event benefiting Children's Hospital Los Angeles on Thursday night (21Apr16). "I love this song! This song's important to us and the fact that we wrote it together is so important to both of us."

With regard to the songwriting process with the Hollaback Girl singer, Blake admits that he sometimes felt "insecure". But despite coming from two different musical worlds, the couple felt an instant easiness together in the studio that made writing and recording the duet extra special.

"I think Gwen has a smaller circle too when it comes to writing, and the fact that we went there that early as we were getting to know each other, it's just remarkable," he shared.

The 39-year-old also gushed about Gwen, calling her "the coolest girl in the world," although he did divulge that he was quite nervous to be singing with the former No Doubt frontwoman.

"I'm intimidated by Gwen all the time," he joked.

Blake's comments come after The Voice coach debuted the cover art for his new album on Monday night's (18Apr16) episode of the U.S. talent show, Gwen is a former coach on the show. On Tuesday (19Apr16), Gwen, 46, took to Twitter to reveal the project's 15 song titles.

"Look what I found lying 'round the house!" she exclaimed as she shared a photo of the back of his new CD, adding the hashtags "#ispymyname" and "#goaheadandbreakmyheart", the name of a duet between the two lovebirds.

The stars became a couple last October (15), two months after Gwen announced she was divorcing her husband of 13 years, Bush rocker Gavin Rossdale, amid rumours of his infidelity. She turned to Blake for comfort as he was also newly-single following his July (15) divorce from singer Miranda Lambert.